Random number generator and method for same

ABSTRACT

A method and system for generating random numbers is disclosed wherein an array of imaging sensors while not in normal use, captures ambient light and back scattered light. These light sources vary naturally over a range of intensities. Intensity values above and below a threshold value are decoded as “1” and “0” bits, respectively. The resulting values, based on noise within the array signal, are single bit values or n bit values. A preferred imaging sensor array is a charge coupled device. Other imaging sensor arrays such as capacitive fingerprint imagers may also be used for this purpose when sufficient noise exists within the imaging sensor array signal.

This is a continuation-in-part from U.S. patent application Ser. No.09/023,460 filed Feb. 13, 1998 U.S. Pat. No. 6,215,874 which furtherclaims priority from U.S. patent application Ser. No. 08/728,549 filedOct. 9, 1996, now abandoned (ABN).

FIELD OF THE INVENTION

This invention relates generally to random number generation and moreparticularly relates to a method of generating a number within a randomsequence of numbers using noise presented to or from within a chargecoupled device (CCD) or the like.

BACKGROUND OF THE INVENTION

Computer security is fast becoming an important issue. With theproliferation of computers and computer networks into all aspects ofbusiness and daily life —financial, medical, education, government, andcommunications —the concern over secure file access is growing. Onemethod of providing security from unauthorized access to files is byimplementing encryption and cipher techniques. These techniques convertdata into other corresponding data forms in a fashion that isreversible. Once encrypted, the data is unintelligible unless firstdecrypted. RSA, DES, PGP, and CAST are known encryption techniques thatare currently believed to provide sufficient security for computercommunications and files.

Each of these encryption techniques uses a key or cipher. Such a key iscrucial to the encryption/decryption process. Anyone with a correct key,can access information that has previously been encrypted using thatkey. The entry of the key from the keyboard is impractical since a keyremembered by a user for entry is liable to be discovered by anindividual desiring unauthorized access to existing encrypted files.

In DES encryption, the key is a numerical value, for example 56 bits inlength. Such a key can be used to encrypt and subsequently to decryptdata. The security of the data once encrypted is sufficient that the keyis required to access the data in an intelligible form. Thus, thesecurity of the data is related to the security of the key.

In an optical fingerprint input transducer or sensor, the finger underinvestigation is usually pressed against a flat surface, such as a sideof a glass plate, and the ridge and valley pattern of the finger tip issensed by a sensing means such as an interrogating light beam.

Various optical devices are known which employ prisms upon which afinger whose print is to be identified is placed. The prism has a firstsurface upon which a finger is placed, a second surface disposed at anacute angle to the first surface through which the fingerprint is viewedand a third illumination surface through which light is directed intothe prism. In some cases, the illumination surface is at an acute angleto the first surface, as seen for example, in U.S. Pat. Nos. 5,187,482and 5,187,748. In other cases, the illumination surface is parallel tothe first surface, as seen for example, in U.S. Pat. Nos. 5,109,427 and5,233,404. Fingerprint identification devices of this nature aregenerally used to control the building-access or information-access ofindividuals to buildings, rooms, and devices such as computer terminals.

In capacitive fingerprint imaging devices, a fingertip is pressedagainst an array of sensing electrodes. Each electrode forms one of twoelectrodes in a capacitor. Each capacitor is generally pre-charged toprovide a known voltage. The placement of the fingertip on the sensingelectrodes results in changes to the induced voltages or capacitancesand therefore allows for imaging of the fingerprint. Devices of thistype are well known in the art.

The use of random numbers has become popular in many aspects of computerscience. An annealing algorithm generates an entire process based on aninitial random seed. The seed allows the process to be repeated, but itsrandom nature allows the annealing process to run differently each time.In encryption technology, random keys are also used for generatingprivate and public keys. Unfortunately, computers are only capable ofgenerating pseudo random numbers. These numbers may follow knownsequences or they may rely on date and time information making thempredictable.

Several electronic approaches to random number generation have beenproposed. It is known to use a resistive circuit that generates avoltage or current to be measured that lies at an exact value. Voltagesabove and below the value are interpreted as a one and a zero,respectively. Of course, it will be apparent to those of skill in theart that the selection of one to be above the threshold is arbitrary andthat the respective interpretation can be otherwise. The random natureof the binary value is ensured based on the laws of quantum physics.Unfortunately, such a system is influenced by external factors such astemperature, humidity, etc. Also, electronic random number generatorsfor use with a computer are often costly.

When conditions change, existing devices often become unreliable. Forexample, a resistance based device often produces a sequence of “random”numbers of a dubious nature when temperature changes are significant. Asis well known, this is often the case within computer systems, wherebright lights are used, near doorways, in electronic devices, inautomobiles, and so forth. As such, a more flexible random numbergenerating device and method is needed.

It is, therefore, an object of this invention to provide a costeffective means of generating a number within a random sequence ofnumbers having a configurable distribution.

It is further an object of the invention to provide means of generatinga number within a random sequence of numbers using already existingdevices connected to a computer and used for other purposes such asbiometric input devices or touchpads.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided, a method ofgenerating a number within a random sequence of numbers using an imagingdevice comprising a transparent layer for transmitting impinging lightof an image provided to the imaging device and an array of imagingsensors within an integrated circuit affixed to a layer of substrate forsensing the transmitted light, the method comprising the steps of:

sensing with the array of imaging sensors an image provided to thedevice;

providing image data corresponding to the sensed image, wherein theimage data comprise an array of pixels, each pixel provided by oneimaging sensor of the imaging sensor array; and,

if no image is provided to the device:

sensing, with a first imaging sensor, a first signal to provide firstsensed data,

wherein at least a portion comprises noise presented to or from withinthe device;

sensing, with a second imaging sensor, a second signal to provide secondsensed data, wherein at least a portion comprises noise presented to orfrom within the device;

determining a noise based value from the noise portion within each ofthe first sensed data and the second sensed data; and, based on thenoise based value providing the number within the random sequence ofnumbers.

A further embodiment comprises the additional steps of:

sensing, with a third imaging sensor, a third signal to provide thirdsensed data, wherein at least a portion comprises noise presented to orfrom within the device;

sensing, with a fourth imaging sensor, a fourth signal to provide fourthsensed data, wherein at least a portion comprises noise presented to orfrom within the device;

determining a first noise based value from the noise portion within eachof the first sensed data and the second sensed data;

determining a second noise based value from the noise portion withineach of the third sensed data and the fourth sensed data;

based on the second noise based value modifying the first noise basedvalue; and,

based on the modified noise based value providing the number within therandom sequence of numbers.

In accordance with another aspect of the invention there is furtherprovided a method of generating a number within a random sequence ofnumbers using an imaging device comprising a transparent layer fortransmitting impinging light of an image provided to the imaging deviceand an array of imaging sensors within an integrated circuit affixed toa layer of substrate for sensing the transmitted light, the methodcomprising the steps of:

sensing with the array of imaging sensors an image provided to thedevice;

providing image data corresponding to the sensed image, wherein theimage data comprise an array of pixels, each pixel provided by oneimaging sensor of the imaging sensor array; and,

if no relevant image information is provided to at least two imagingsensors of the array of imaging sensors;

sensing, with a first imaging sensor of the at least two imagingsensors, a first signal to provide first sensed data wherein at least aportion comprises noise presented to or from within the device;

sensing, with a second imaging sensor of the at least two imagingsensors, a second signal to provide second sensed data wherein at leasta portion comprises noise presented to or from within the device;

determining a noise based value from the noise portion within each ofthe first sensed data and the second sensed data; and,

based on the noise based value providing the number within the randomsequence of numbers.

In accordance with yet another aspect of the invention there is provideda method of generating a number within a random sequence of numbersusing a device comprising an array of sensing electrodes, each sensingelectrode being one of a pair of electrodes forming a capacitor, themethod comprising the steps of:

sensing with the array of sensing electrodes an image of an object incontact with or in close proximity of the device, wherein the sensingelectrodes sense a change of capacitance induced by the object;

providing image data corresponding to the sensed image by measuring thechange of capacitance; and,

if no image is provided to the device:

sensing, with a first sensing electrodes, a first signal to providefirst sensed data, wherein at least a portion comprises noise presentedto or from within the device;

sensing, with a second sensing electrodes, a second signal to providesecond sensed data, wherein at least a portion comprises noise presentedto or from within the device;

determining a noise based value from the noise portion within each ofthe first sensed data and the second sensed data; and,

based on the noise based value providing the number within the randomsequence of numbers.

In accordance with the invention there is provided an imaging deviceused for generating a number within a random sequence of numberscomprising:

a transparent layer for transmitting impinging light in dependence uponan image provided to the imaging device;

an array of imaging sensors within an integrated circuit affixed to alayer of substrate for sensing the transmitted light and for providingan array of pixels corresponding to the sensed image, each pixelprovided by one imaging sensor of the imaging sensor array andcomprising a signal in dependence upon input information provided to theimaging sensor, wherein at least a portion of the signal comprises whitenoise presented to or from within the imaging sensor; and,

a processor for receiving the signals from at least two imaging sensorsof the imaging sensor array and for determining a value based on theportions of the signals comprising white noise.

In accordance with another aspect of the invention there is provided adevice used for generating a number within a random sequence of numberscomprising:

an array of sensing electrodes, each sensing electrode being one of apair of electrodes forming a capacitor, for sensing an image of anobject in contact with or in close proximity of the device by sensing achange of capacitance induced by the object and for providing image datacorresponding to the sensed image; and,

a processor for receiving the signals from at least two sensingelectrodes of the array of sensing electrodes and for determining avalue based on the portions of the signals comprising white noise.

The advantages of a system in accordance with this invention arenumerous. For example, random number generation will vary effectivelyfrom computer to computer thereby decreasing chances of predictingrandom number values.

It is a significant advantage that a device according to the inventionis capable of calibration and reconfiguration during normal use.

It is a significant advantage of the present invention that a singlesensor array serves multiple purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention will now be discussed inconjunction with the attached drawings in which:

FIG. 1 is a block diagram of a known biometric sensing device with anadditional diffusing cover thereon according to the present invention;

FIG. 1a is a schematic diagram of a charged coupled device;

FIG. 2 is simplified diagram of a capacitive fingerprint imaging device;

FIG. 3 is a simplified diagram of an optical fingerprint imaging devicewith an additional diffusing cover thereon according to the presentinvention;

FIG. 4a is a flow diagram of a method according to the presentinvention;

FIG. 4b is a flow diagram of another method according to the presentinvention;

FIG. 4c is a flow diagram of another method according to the presentinvention;

FIG. 4d is a flow diagram of yet another method according to the presentinvention;

FIG. 4e is a flow diagram of yet another method according to the presentinvention; and

FIG. 5 is a flow diagram of a method of calibrating a device accordingto the present invention.

DETAILED DESCRIPTION

Throughout the specification and claims, the term a number within arandom sequence of numbers is defined to mean a number that is notpredictable. For example, the definition of random number generation inthe Computer Dictionary, 1993, Microsoft Press is “The creation of anumber or sequence of numbers characterized by unpredictability so thatno number is any more likely to occur at a given time or place in thesequence than any other.” Of course this refers to a random numbergenerator producing a flat distribution of random values. Otherdistributions are known and do not reduce the random nature of thesequence. For example, a die with two faces having a 1 thereon has twicethe likelihood of resulting in a 1 and yet results in a random sequencewhen thrown repeatedly. A random number as defined above, is a number ina sequence of numbers wherein the sequence exhibits certain statisticalbehaviors. For example, a random sequence generated by a random numbergenerator is non-repeating, non-predictable, and non-reproducible.

The term non-deterministic random number is defined to mean a numberthat is not determinative based solely on an input to a system and formsa subset of random numbers.

A pseudo-random number is a deterministic number determined in a fashionthat causes it to appear random when in fact it is not; it is repeatablydetermined and given a seed value, can be regenerated using a samepseudo-random number generator

A near random number is a number that is a random number but that doesnot subscribe to a desired distribution either because the distributionvaries over time or because it is statistically predictable in some way.

A device, shown in FIG. 1, comprises a biometric sensing device 1through which biometric input in the form of a fingerprint is received.Similar devices absent the diffusing cover 20 are known in the art ofbiometric sensing. In use a fingertip is placed on the biometric sensingdevice 1 and illuminated. Light from a light source 6 is refledted bythe fingertip and is then reflected off several mirrors 12 prior topassing through a lens 13 to focus upon an imaging device 2, such as acharge coupled device (CCD). The number of mirrors used is optional butis chosen so as to limit other light sources (noise) and to limit imagedegradation. Alternatively, no mirrors are present and the lightreflected by the fingertip is passed directly through the lens 13. Thelens 13 is spaced from the CCD 2 so that an image is focused upon theCCD 2. Such optical focus is well known in the art.

Referring to FIG. 1a a schematic diagram of a CCD 2 is shown. The CCD 2comprises an array of imaging sensors 62 (for example an array of200×300) made of light sensitive semiconductor material within anintegrated circuit affixed to a layer of substrate 64 such as silicon.The integrated circuit further comprises connections 66 to each imagingsensor. A light sensitive material often used in CCDs is, for example,doped polysilicon. Photons impinging onto the sensor 62 free electronsfrom the sensor's crystal lattice. Therefore, an electrical signalproportional to the amount of photons, that is, proportional to lightintensity, is provided by the sensor 62 and transmitted via theconnection 66 to address and output generating means 68. The CCD 2further comprises a transparent layer 60 for transmitting the light ofan image onto the array of imaging sensors 62 and for protecting theintegrated circuitry.

Alternatively, a complementary metal oxide semiconductor (CMOS) imagingdevice may be used. The recently developed CMOS imaging device comprisesa similar structure as the CCD shown in FIG. 1a, but it is expected thatuse of different materials provide a significant reduction of productioncosts.

The CCD 2 is capable of converting an incident optical image intoelectrical signals; such use of CCDs is known. Output from the CCD is ananalog electrical signal. The output electrical signal is passed tocircuit 50 which adjusts the signal as necessary to meet a pre-selectedanalog video signal standard which is then transmitted by the circuit 50via the carrier means 7 to a connection means 9 which in turn isconnected to a frame grabber 22. The frame grabber 22 is commonly aperipheral card installed within a computer 10.

When no fingertip is located on the prism 1, the CCD 2 captures ambientlight. Some of this light is from sources external to the biometricscanner. Other light is from a light source within the biometricscanner. Yet another source of captured light is backlight. The exactpercentage from each is unknown and somewhat random within a range ofvalues. Calibration of the device in a particular environment orproviding the device with a cover 20 provides some indication of apercentage of a signal derived from ambient light or light sources and apercentage of light derived from other sources such as noise.

The CCD 2 has a large number of imaging sensors within the device (forexample an array of 200×300) in order to provide sufficient resolutionof an image (for example an array of 200×300 pixels). To generate asingle binary value, all 60,000 pixels can be summed and averaged. Thisvalue will fall between 0 and the depth of the pixels (in value and notin bits). Once calibrated, a value will map onto a bit of “1” or a bitof “0” and therefore result in the selection of a binary random number.

Essentially, the invention relies on the existence of white noise—randomnoise—at the imaging sensors and filters out a known signal of ambientdiffused light or of a known pattern in the case of a device providedwith a cover. The use of a CCD as the imaging device is rendered costeffective both because CCD costs are falling and because a CCD is knownto be used with a computer for other applications such as biometricsensing. Multiple uses of a CCD allow each function to bear only aportion of the cost of the electronic device. Further, the use of a CCDprovides numerous imaging sensors and thereby allows for softwareconfiguration, calibration, and selection of a desired distribution ofvalues for the random sequence.

Referring to FIG. 2, a capacitive fingerprint imager is shown. Similardevices are used in biometric sensing and in touchpads. The imagingdevice comprises an array of sensing electrodes 78 spaced apart toprevent interference. Each sensing electrode 78 forms one of twoelectrodes in a capacitor. The sensing electrodes 78 are pre-charged bya pre-charging circuit 79 to a predetermined voltage. When a fingertipis placed in contact with or in close proximity to the sensingelectrodes 78, the capacitance is changed and this change is measured oroutput by addressing and output generation means 77. As in a CCD, thecapacitive fingerprint imager often has circuitry for addressing eachimaging sensor (sensing electrode and associated circuitry) and forconverting values provided by each imaging sensor into an analogueserial signal provided as an output signal. The output signal is thensampled at a predetermined frequency in order to digitize theinformation and make use of it within a computer or other microprocessorbased device. Alternatively, the signal can be encoded on a non-volatilestorage medium such as magnetic tape for later retrieval.

When used with the present invention, it is desirable that the sensingelectrodes 78 be allowed to float (unconnected to ground) when used forrandom value generation. The floating sensing electrodes 78 result in asignal with a substantial noise component that is suitable for pseudorandom number generation. The signal is sampled at predetermined timesto produce sampled values. Random values are determined in dependenceupon these sampled values. For example, the sampled values are filteredto remove ambient signals (real data) and then the remaining component(substantially noise) is evaluated. When it is above a predeterminedthreshold a “I” bit results. Conversely, when it is below apredetermined value a “0” bit results. It will be apparent to those ofskill in the art that alternatively, a “I” bit may result from a lowervalue and a “0” bit from a higher value.

An embodiment of the invention will now be described in which adiffusing cover 20 is placed over an optical fingerprint sensing devicein order to prevent light flicker, dust, or other variables fromaffecting system operation.

Referring to FIG. 3, an optical fingerprint scanner is shown comprisinga biometric sensing device through which biometric input in the form ofa fingerprint is received, several mirrors 12, a lens 13, and a CCD 2.The number of mirrors used is optional but is chosen so as to limitother light sources (noise) and to limit image degradation when thedevice is used for its intended purpose of fingerprint imaging. Opticalfingerprint devices are known in the art. The biometric input device inthe form of a prism acts to diffuse ambient light. Alternatively adevice according to this invention is provided with a diffusing cover20. The cover acts to diffuse light from external sources evenly acrossthe cover.

In operation, the device is calibrated and an ambient light level isestablished. The calibration is performed at the beginning of each day.Alternatively, the calibration is performed at predetermined intervalsthroughout each day. Imaging sensors within the charge coupled devicereceive approximately equivalent diffused light. At least some imagingsensors are selected for use in random number generation. The imagingsensors are selected randomly. Alternatively, the imaging sensors areselected based on a statistical determination of randomness of generatedvalues. Further alternatively, the imaging sensors are selected based ona pattern of imaging sensor selections.

It is advantageous to use a plurality of imaging sensors as describedherein. Firstly, use of an array of imaging sensors provides flexibilityin use, reliability from failure, and additionally, when a plurality ofimaging sensors such as a CCD array is used, similar imaging sensorinputs are often easily identified to improve performance by simplifyingthe process of extracting random information from imaging sensorsignals.

The selected imaging sensors (as well as all other imaging sensors)receive light diffused by the diffusing cover 20. The imaging sensorsalso receive back-scattered light in the form of noise. The noise issufficient to effect the induced charge in at least some imagingsensors, thereby introducing noise into the CCD signal. The non-noiseportion of the signal is filtered out for the selected imaging sensorsand the remaining signal comprising substantially noise is evaluated.Noise values above a predetermined value are defined as “I” bits whilethose values below a predetermined value are defined as “0” bits.Alternatively, the noise is quantized into a 2 bit, 3 bit, . . . , n bitvalue. Alternatively, the noise is not quantized and is used to generateanalogue random values.

Referring to FIGS. 4a, 4 b, 4 c and 4 d, alternative flow diagrams forthe device are shown. In FIG. 4a, the distinction between a “1” bit anda “0” bit are determined by a threshold value. As such, selected imagingsensors should have no correlation in response to ambient light or anyintended stimulus having a noise component or some other substantiallynon-deterministic and non-repeatable component. Such a lack ofcorrelation may occur when ambient light is constant or truly random, orwhere selected imaging sensors are affected by different ambient lightsources. In FIG. 4a, a method is employed wherein calibration is firstperformed. Thereafter, a signal corresponding to intensity and frequencyof light incident on imaging sensors within the CCD is provided by theCCD and a value corresponding to a predetermined imaging sensor is read.Reading a value is performed by digitizing the signal at an appropriatetime. Alternatively, reading a value is performed by reading a digitalvalue from a memory where it is previously stored. A threshold value asdetermined by the calibration process is compared to the read value. Avalue higher than the threshold value results in a ‘I’ output and avalue lower than the threshold value results in a ‘0’ output.Alternatively, a higher value results in a ‘0’ output and a lower valueresults in a ‘I’ output.

Advantages provided by switching imaging sensors when not random aresignificant. For example, when an imaging sensor is random at times orbecomes stable for a while, switching to other imaging sensors providescontinuous operation. Also, when a data input is provided to an imagingsensor, others potentially have no input. This is common, for example,in biometric contact imagers. Often a fingertip only covers a portion ofa fingerprint scanner, for example. This allows selection of imagingsensors in corners of the imaging device wherein data input is often notprovided. Of course, flexibility, reliability and ease of calibrationremain significant advantages. Also, selection of a distribution for thegenerated sequence of random numbers is enabled according to the presentmethod.

Referring to FIG. 4b, a flow diagram is shown for use with a CCD in theform of a video camera, optical fingerprint sensor, or other device usedwith a computer. During use, the device captures images of externalobjects and as such, there is likely a strong similarity between signalsfrom adjacent imaging sensors within the CCD. The use of a method asexemplified by the diagram of FIG. 4a would result in “random numbers”of dubious quality. According to the method of FIG. 4b, the signalpresent at each imaging sensor within the CCD is measured at a highenough precision to be a measure of substantially white noise. Forexample, if we were to filter out all values up to 9 decimal placeswithin the ambient signal, the resulting decimal value fluctuates inaccordance with white noise and is therefore likely random.

Persons of skill in the art, would be able to test for randomness. Onesuch series of tests is set out in Knuth, Donald E. The Art of ComputerProgramming, Seminumerical Algorithms Vol. 2, Addison Wesley, 1969 onpages 1-155. The analysis of the random nature of the sequences ofgenerated values is a straightforward test requiring mereexperimentation and verification. For example, a series of numbers issaid to be random when a sufficiently large number of the numbers in theseries exhibit randomness. The numbers will average to the average ofthe desired distribution, have the desired distribution —appropriatestandard deviations etc., do not follow a discernable pattern —twentyones then twenty zeros —and so forth. Testing a device to evaluaterandomness and quality of random number generation is a mere experimentand statistical analysis. Performing such an experiment and analysisallows for better selection of a filter function and a suitablethreshold.

Though, for testing randomness of numbers, Knuth is suggested herein, itis solely as a reference for that purpose. Knuth provides adequateexplanation of random number testing including frequency of occurrenceof given numbers, average, standard deviation, variation over time,etc.; however, the specific definition of random number presentedtherein is not incorporated herein.

Referring to FIG. 4c, a further method of using white noise provided toor from within a plurality of imaging sensors is shown. Such a method isbest applied when two imaging sensors receive substantially the sameinformation. This is so when two microphones are placed side by side, insome adjacent imaging sensors of a CCD array, or in most imaging sensorsof a CCD array when provided with light from a same source or whenfocused on a uniform surface. Signals from adjacent imaging sensors orother imaging sensors receiving substantially same information are readand their values subtracted to form a signal representative ofsubstantially the white noise of one signal from one imaging sensorminus the white noise of a signal from the adjacent imaging sensor. Whenambient light is present (as is the case with an optical fingerprintsensing device provided with a cover or a video camera with a diffusioncovering) and no discernible non-linearities exist within the CCD fieldof view, each imaging sensor provides an information signal that issubstantially similar to signals provided by adjacent imaging sensors.The main difference between signals from adjacent imaging sensors isattributable to noise. When such is the case, the method produces randomvalues of good quality. Alternatively, when such is the case a value isread from each of two imaging sensors and the values are compared. Thecomparison results in a ‘0’ for less than and in a ‘1’ for greater than.Equivalent values are either grouped into ‘1’ or ‘0’ or are treated as aspecial case, or alternatively, are included within one of the twoprevious cases.

There is a significant advantage to using a plurality of signalscomprising noise to determine a random number, the signals from aplurality of imaging sensors. For example, the use of two signalsprovides a mix of two random noise values. The use of 100 signalsprovides a mix of 100 random noise signals. Statistically, the use ofmany random noise signals results in a random value even when some ofthose signals become somewhat deterministic or the noise therein isnominal over a period of time. As such, reliability is enhanced.

Also, the use of a number of signals from a number of different imagingsensors results in configurability not known in the prior art.Distributions become configurable by selecting and weighting differentvalues determined based on noise portions of different signals to resultin a desired distribution. This provides for a random number generatorand method of generating random numbers that allows for different randomnumber functions to be supported by a same physical device.

For example, when a distribution having a 90% chance of providing avalue from 0-1 and a 10% chance of providing a value from 1-2 isdesired, a first pair of signals is used to generate a random number. Asecond pair of signals is used to generate a second random number. Eachrandom number has a flat distribution from 0 to 1. When the secondrandom number is above 0.9, 1 is added to the first random number. Theresulting value has the desired distribution. Of course, the signals areselected so that noise portions of the different signals are dissimilarand unrelated. Optionally, more than two signals are used for generatingeach random number. It is evident to those of skill in the art, thatmany simple and very complex random number distributions are supportedby such a device.

Referring to FIG. 4d, a further method of using the white noise is shownwherein signals from each of a plurality of imaging sensors are sampledand signal values are added to form a single value based on the outputfrom a group of imaging sensors. The result is then compared to athreshold value to determine a random value, which is output.Alternatively, the result is further transformed prior to determining arandom value. One form the further transformation can take issubtracting out higher order digits in order to limit the value to anon-ascending value; preferably, this value is comprised mostly ofnoise.

Referring to FIG. 4e, a further method of using white noise is shownwherein a signal from each of a plurality of imaging sensors is sampledand the sampled values are subtracted from values of sampled signalsfrom same or similar imaging sensors from another time. For ambientlight, images often remain relatively constant with the exception ofslight variations and noise. Using a subtractive method of imagingsensors from a present frame from imaging sensors of a past frame (orvice versa), allows the constant nature of the frames to be exploitedfor extracting noise from images. The result is then compared to athreshold value to determine a random value, which is then output.Alternatively, the result is further transformed prior to determining arandom value. One form the further transformation can take issubtracting out higher order digits in order to limit the value to anon-ascending value; preferably, this value is comprised mostly ofnoise.

Preferably, a combination of methods is concurrently available within adevice or on a host computer and the selection of the method is based ona statistical analysis of randomness of the device. Alternatively, auser selects the method employed. Further alternatively, the methodemployed is predetermined.

It will be clear to those of skill in the art that the use of adiffusing cover is optional. In spaces where ambient light is random orrelatively constant, said cover is obviated. Also, where the inputdevice is already provided with diffusing means or means for performinga similar function, a further cover is unnecessary. It will be clear tothose of skill in the art that relocating such a device requiresre-calibration.

Advantageously, the device is an adaptation of an existing device. Forexample, another embodiment will now be described with reference to FIG.1. When the diffusing cover 20 is replaced with a non-transmissivecover, light from the light source 6 is reflected off a platen surfaceof the prism 1 toward the mirror 12 and via an optical path to theimaging sensor array 2. The information content of such a signal issubstantially uniform over areas of the CCD 2, and therefore over aplurality of adjacent imaging sensors. A noise portion of signals fromthose imaging sensors is a result of noise within the light source,noise from backscattered light, and other noise sources within thedevice such as inductance, capacitance, temperature, air and so forth.Using the method of FIG. 4c or FIG. 4e is particularly advantageous withsuch a configuration. Of course, the methods of FIGS. 4a, 4 b, or 4 dare also applicable.

It will be clear to those of skill in the art that the use of anon-transmissive cover is optional when the prism 1 is substantially orat least partially reflective and wherein light from outside the devicedoes not substantially affect the captured image. Alternatively, whenlight from outside the device does substantially affect the capturedimage, a method of filtering that light is used.

Referring to FIG. 5, a flow chart of a method of calibrating a systemaccording to the present invention is shown. The system is initialized.This sets the imaging sensor array into a normal mode of operation forcapturing images. A plurality of images is captured while the device isnot in normal use. When a cover is used, the cover is in place prior tocapturing the plurality of images. For each imaging sensor an averagevalue is determined. Alternatively, standard deviation, average andmedian values are determined to ensure that the threshold value selectedis statistically correct. The randomness of the values read is analyzed.This analysis includes testing for correlation among adjacent imagingsensors and distribution. Signals from any imaging sensors, which arenot sufficiently random (as determined by user preference settings), arenoted and associated imaging sensors are blocked out. These imagingsensors are not used by the system, at least until user preferences arechanged or re-calibration occurs. The averages are stored for eachimaging sensor excepting those blocked out as threshold values.Alternatively, other values determined to be more statistically correctare stored as threshold values. Once threshold values are determined,the system is placed in a normal mode of operation.

Alternatively, when threshold values are not used, calibration isperformed to verify the randomness of the noise within an imaging sensorarray and to establish any correlations between imaging sensors withinthe array. Established correlations are then used to determine imagingsensor groupings and an applicable method of extracting noise from thesignals. Further alternatively, no calibration is performed.

Where sufficient noise exists, similar methods to those set out areemployable during normal use of an imaging sensor array. For example, afingerprint sensor images a fingertip and subtracts the image from otherimages of the same fingertip in order to achieve a signal in dependenceupon which random values are generated. Alternatively, pseudo randomnumbers are determined in dependence upon a specific bit or a specificdigit within at least a value determined in dependence upon at least asignal from the imaging sensor array.

The random numbers generated according to the present invention areuseful as seeds to pseudo-random number generators. For example, in anannealing process, it is useful to generate a random pseudo-randomnumber. This is accomplished by generating a random seed. The seed isthen provided to the user for repeating the same annealing process at alater time. Pseudo-random number generators are well known and aretherefor not more fully described herein.

The invention relies on the use of an existing device connected to acomputer, such as an imaging device for imaging or a touchpad for movinga cursor, for providing a signal comprising noise for use in randomnumber generation.

Further, the invention relies on noise at each of a plurality of imagingsensors to generate a random value having a desired distribution andother desired properties. The use of a plurality of imaging sensors in aconfigurable fashion as described herein is not known in the art.

In an embodiment, when a normal distribution of values is desired from arandom number generator according to the invention, signals from eachnon-blocked imaging sensor are sampled and a distribution of noisewithin each signal is evaluated. Those signals that when combined resultin noise having a substantially normal distribution are noted. Thosesame signals are then sampled during random number generation. Asignificant advantage of the present invention is that reconfiguring therandom number generator requires little skill and no hardwaremodifications. To change the random number generator from a sequencehaving a normal distribution to one having a flat distribution requiresselection of this option and possibly a re-calibration of the device.

Alternatively, several distributions are calibrated simultaneously andthen a user selects a distribution as desired. As such, a calibrationprocess may store five or six different distributions and the signalsdetermined necessary for achieving those distributions. Upon selectingany of the distributions, the random number generation proceeds based onthe determined signals.

Numerous other embodiments may be envisaged without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method of generating a number within a randomsequence of numbers using an imaging device comprising an integratedcircuit, the integrated circuit having a plurality of imaging sensors ina known arrangement for sensing an image provided thereto and forproviding an output signal indicative of the sensed image, wherein theoutput signal comprises a plurality of pixel values each relating to animaging sensor from the plurality of imaging sensors, each pixel valueof the plurality of pixel values relating to one pixel within the sensedimage at a known location dependent upon the location of the relatedimage sensor, the method comprising: sensing, with a first imagingsensor of the plurality of imaging sensors, a first signal to providefirst sensed data, wherein at least a portion of the first sensed datacomprises noise presented to or from within the device; sensing, with asecond imaging sensor of the plurality of imaging sensors, a secondsignal to provide second sensed data, wherein at least a portion of thesecond sensed data comprises noise presented to or from within thedevice; determining a noise based value from the noise portion withineach of the first sensed data and the second sensed data; and, based onthe noise based value providing the number within the random sequence ofnumbers.
 2. A method of generating a number within a random sequence ofnumbers as defined in claim 1, comprising: comparing the noise basedvalue to a threshold value and providing a first binary value when thenoise based value is below the threshold value and a second differentbinary value when the noise based value is above the threshold value. 3.A method of generating a number within a random sequence of numbers asdefined in claim 1, comprising: removing higher order digits from thenoise based value and retaining lower order digits within the noisebased value to provide the number.
 4. A method of generating a numberwithin a random sequence of numbers as defined in claim 1, wherein thestep of determining a first noise based value comprises: subtracting avalue derived from the first sensed data from a value derived from thesecond sensed data to provide a difference therebetween, wherein thedifference is provided as the number within the random sequence ofnumbers.
 5. A method of generating a number within a random sequence ofnumbers as defined in claim 1, comprising: extracting a combined noiseportion from the first sensed data and from the second sensed data; and,sampling the combined noise portion to produce a sampled value, whereinthe number is determined in dependence upon the sampled value.
 6. Amethod of generating a number within a random sequence of numbers asdefined in claim 1, wherein the step of determining a first noise basedvalue comprises: determining a primary value based on the noise portionwithin the first sensed data; determining a secondary value based on thenoise portion within the second sensed data; and, based on the primaryvalue modifying the secondary value to provide the number.
 7. A methodof generating a number within a random sequence of numbers as defined inclaim 6, wherein modifying the secondary value comprises adding anamount to the secondary value, the amount determined in dependence uponthe primary value.
 8. A method of generating a number within a randomsequence of numbers as defined in claim 6, wherein modifying thesecondary value comprises determining a range of values for thesecondary value in dependence upon the primary value.
 9. A method ofgenerating a number within a random sequence of numbers using an imagingdevice comprising an integrated circuit, the integrated circuit having aplurality of imaging sensors in a known arrangement for sensing an imageprovided thereto and for providing an output signal indicative of thesensed image, wherein the output signal comprises a plurality of pixelvalues each relating to an imaging sensor from the plurality of imagingsensors, each pixel value of the plurality of pixel values relating toone pixel within the sensed image at a known location dependent upon therelated image sensor, the method comprising: sensing with the pluralityof imaging sensors an image provided to the device; providing an outputsignal based on the sensed image; and, In the absence of relevant imageinformation at at least two imaging sensors of the plurality of imagingsensors: sensing, with a first imaging sensor of the at least twoimaging sensors, a first signal to provide first sensed data wherein atleast a portion comprises noise presented to or from within the device;sensing, with a second imaging sensor of the at least two imagingsensors, a second signal to provide second sensed data wherein at leasta portion comprises noise presented to or from within the device;determining a noise based value from the noise portion within each ofthe first sensed data and the second sensed data; and, based on thenoise based value providing the number within the random sequence ofnumbers.
 10. A method of generating a number within a random sequence ofnumbers as defined in claim 9, wherein the relevant image informationcomprises fingerprint image data and wherein the at least two imagingsensors of the plurality of imaging sensors are placed outside an areaof the image typically covered by a fingerprint.
 11. A method ofgenerating a number within a random sequence of numbers using a devicecomprising a plurality of sensing electrodes in a known arrangement,each sensing electrode being one of a pair of electrodes forming acapacitor, for sensing an image of an object in contact with or in closeproximity of the device, wherein the sensing electrodes sense a changeof capacitance induced by the object, and for providing an output signalbased on the sensed image, wherein the output signal comprises aplurality of pixel values, each pixel value of the plurality of pixelvalues relating to one pixel at a known location within the sensedimage, the method comprising: sensing, with a first sensing electrode ofthe plurality of sensing electrodes, a first signal to provide firstsensed data, wherein at least a portion comprises noise presented to orfrom within the device; sensing, with a second sensing electrode of theplurality of sensing electrodes, a second signal to provide secondsensed data, wherein at least a portion comprises noise presented to orfrom within the device; determining a noise based value from the noiseportion within each of the first sensed data and the second sensed data;and, based on the noise based value providing the number within therandom sequence of numbers.
 12. An imaging device used for generating anumber within a random sequence of numbers comprising: a transparentlayer for transmitting impinging light in dependence upon an imageprovided to the imaging device; a plurality of imaging sensors in aknown arrangement within a single integrated circuit for sensing thetransmitted light and for providing an output signal based on the sensedimage, wherein the output signal comprises a plurality of pixel values,each pixel value of the plurality of pixel values relating to one pixelat a known location within the sensed image, and wherein at least aportion of the signal comprises white noise presented to or from withinthe imaging device; and, a processor for receiving the signals from atleast two imaging sensors of the imaging sensor array and fordetermining a value based on the portions of the signals comprisingwhite noise.
 13. An imaging device used for generating a random numberas defined in claim 12, wherein the processor is for receiving thesignals and for selectively determining at least two values based on anoise portion of each of the signals and wherein the random number isgenerated in dependence upon the two values.
 14. An imaging device usedfor generating a random number as defined in claim 12, wherein theimaging device comprises a CCD array for sensing an image and forproviding a signal including pixel values for pixels of the sensed imagein each of a plurality of rows and columns.
 15. An imaging device usedfor generating a random number as defined in claim 12, wherein theimaging device comprises a CMOS imaging device.
 16. A device forgenerating a random number as defined in claim 14, comprising: a prismincluding a platen for accepting a fingerprint; a light source fordirecting light toward the platen, a portion of the light reflecting offthe platen along an optical path, wherein the charge coupled devicearray is disposed within the optical path to provide signals independence upon light within the optical path incident thereon.
 17. Adevice for generating a random number as defined in claim 16, comprisinga cover for the platen, said cover for rendering the platensubstantially reflective.
 18. A device used for generating a numberwithin a random sequence of numbers comprising: a plurality of sensingelectrodes in a known arrangement, each sensing electrode being one of apair of electrodes forming a capacitor, for sensing an image of anobject in contact with or in close proximity of the device by sensing achange of capacitance induced by the object and for providing an outputsignal based on the sensed image, wherein the output signal comprises aplurality of pixel values, each pixel value of the plurality of pixelvalues relating to one pixel at a known location within the sensedimage; and, a processor for receiving the signals from at least twosensing electrodes of the array of sensing electrodes and fordetermining a value based on the portions of the signals comprisingwhite noise.
 19. A device for generating a random number as defined inclaim 18, wherein the plurality of sensing electrodes is arranged in aplurality of rows and a plurality of columns each row being related to arow in the sensed image and each column being related to column in thesensed image.
 20. A device for generating a random number as defined inclaim 19, wherein the plurality of sensing electrodes is a touchpad.